1. Field of the Invention
The present invention is directed to an organic polymer supported olefin polymerization catalyst component. More particularly, the present invention concerns a catalyst system, useful in the polymerization of olefins, which includes a catalyst component supported on a copolymer of an olefin and an unsaturated silane.
2. Background of the Prior Art
The polymerization of olefins is one of the most commercially important processes in the chemical industry. This importance is manifested in the extensive patent and technical literature devoted to this important process.
One aspect of this process, upon which particular attention has been focused, is the development of new and improved catalyst components and catalyst systems to provide improved olefinic polymers. One of the ways of developing new and improved catalytic components is the design of new supports. The development of new supported olefin polymerization catalysts has long been known as a fruitful means of obtaining improved performance of catalyst components. This is so since catalytic agents disposed on a support provide improved catalytic performance compared to the same catalytic agents employed in their unsupported state. This improved performance is manifested in higher catalytic activity and the production of polymers having enhanced properties.
In the prior art olefinic polymerization catalysts, including Ziegler-Natta catalysts, were usually supported on inert inorganic oxides such as silica, alumina, magnesia and the like. Such oxides, which come in a variety of particle sizes and porosities, are often credited with the above-described improvements in catalytic behavior.
Despite their usefulness, inorganic oxide supports have serious deficiencies. Succinctly put, they suffer from their inherent physical properties and their incompatibility with the product of the process in which they are employed, an olefin polymer.
In regard to the inherent physical property limitations of inorganic oxide supports, inorganic oxides adsorb water on their surfaces. Water is a well known catalytic poison which adversely affects catalytic activity. Thus, inorganic oxides, employed as supports, must be calcined at high temperatures, treated with appropriate compounds or both to remove physically adsorbed water from their surfaces prior to their use as an olefin polymerization catalyst component support.
Another adverse physical characteristic of inorganic oxides is their limited maximum pore size. Catalytic activity is directly proportional to pore size. It is true that inorganic oxides having large pore sizes are known. However, these oxides are friable and their use as catalytic supports is discouraged because they, through attrition, form undesirable fines.
Inorganic oxides not only adsorb water on their surface but also other undesirable catalytic poisons including oxygen. Thus, great care must be exercised in handling inorganic oxide supported catalyst components.
Inorganic oxides are incompatible with the product of the catalyzed reaction, organic polymers. As such, the supported catalyst component, which is included in the polymeric product, represents an undesirable containment therein. This may be a minor problem or a significant problem depending upon the catalytic activity of the catalyst system.
To overcome the above deficiencies of inorganic oxide supports in olefin polymerization catalyst components many investigators have developed polymeric supports in their stead. To merely illustrate these catalyst supports, they include the supports of U.S. Pat. Nos. 3,772,261; 4,098,979; 4,174,664; 4,268,418; 4,329,255; 4,404,343; 4,407,727; 4,568,730; 4,900,706; 4,921,825; 5,051,484; 5,118,648; 5,244,855; and 5,275,993. Many foreign patents describing polymeric supports, can be mentioned but they are merely cumulative of the supports mentioned in the aforementioned U.S. patents.
There has been a similar manifestation of interest in polymeric supports for olefin polymerization catalyst components in the non-patent technical literature. The following references illustrate recent developments in this technology: Dyachkovskii. et al., J. Poly. Sci., Poly. Sym., 68:97 (1980); Dyachkovskii et al. in "Transition Metals and Organometallics as Catalysts for Olefin Polymerization," Kaminsky and Sinn, Eds., Springer-Verlag, Berlin, 1988 at pp. 67-68; Bochkin et al., Reactive Polymers, 9:99 (1988); Pomogails et al., Poly. Sci., 36:535 (1994); Sun et al., Stud. in Surf. Sci., 89:81 (1994); Sun et al., J. Poly. Sci.: Part A: Poly. Chem., 32:2127 (1994); and Sun et al., J. Poly. Sci.: Part A: Poly. Chem., 32:2135 (1994).
These and many other references disclose various and sundry supports for polymeric catalyst components. These supports, which are formed of polyolefins, usually polyethylene or polypropylene, polystyrenes, polyvinyl alcohols, poly(styrene-divinylbenzene), poly(methylmethacrylate) and the like, share several advantages over inorganic oxide supports.
With the exception of the Dyachkovskii et al. article in Volume 68 of J. Poly. Sci., Poly. Sym. none of the aforementioned references mention silane functionalized olefin polymers as a support. Dyachkovskii et al. describes such a support wherein silane functionality is incorporated by reacting an olefin polymer having pendant hydroxyl groups with a silane compound having the generic formula R.sub.2 SiCl.sub.2.
What is common to the above disclosures is the advantages provided by polymeric supports. For one thing, polymeric supports usually require no dehydration prior to their use. Moreover, they can be easily functionalized so that they can be specially tailored to the particular needs of the active catalytic materials and the particular polymerization reaction desired. That is, they can be prepared such that the catalyst component can have specifically desired porosity, morphology and size controls. Finally, they can be provided at lower cost than equivalent inorganic oxide supports. All of these advantages are obtained without any compromise in the inertness of the support, a major reason for using inorganic oxides in this application.
A major problem associated with the use of organic polymer supports in the prior art, however, has been the inability of providing a sufficient number of functional groups on the surface of the support to insure anchoring of the catalytic agents disposed thereon. That is, such well known inorganic oxide supports as silica provide Si--OH and Si--OR functional groups for supporting transition metal compounds as well as reacting with silicon-, aluminum- and magnesium-containing compounds. In the past, polyethylene supports usually suffered from an inadequate concentration of surface-functional groups necessary to anchor the catalytically active components disposed thereon. As a result, polymeric supports, including polyolefin supports, because the concentration of functional groups on its surface could not support a sufficient concentration of active catalytic agents, to insure the desired degree of catalytic activity necessary to provide adequate productivity, produced supported catalysts with unacceptable levels of catalytic productivity.
Another problem associated with organic polymeric supports for olefin polymerization catalyst components in the prior art has been the inability to polymerize olefins such that the particle product had large spherical shape. Such a shape, as those skilled in the art are aware, significantly enhances the polymerization process, especially when conducted in the gas phase. Large uniformly spherical shaped particles permit the utilization of higher fluidization velocities since large spherical shaped particles are not entrained by the gaseous stream and removed from the reactor.
Moreover, large spherically shaped particles are more easily processed since the problem of fines, i.e. very small sized particles, which cause plugging in the transport of the polymeric product, is eliminated.
Finally, large uniform spherically shaped particles may obviate the costly step of pelletizing the polymeric product.
Of particular interest to the present invention is U.S. Pat. No. 5,209,977 to Heimberg et al. That patent describes a substantially spherical crosslinkable and/or crosslinked ethylene copolymer ranging in size from about 10 microns up to about 500 microns. The '977 patent is further directed to a process for preparing that sized powder and to a process of crosslinking the thermoplastic powder to reduce its melt flow rate.
These polymeric powders are described in the '977 patent as useful as coatings. Such coatings may be applied by dip coating, in either a static or fluidized bed, or by powder coating. The powders of the '977 patent may be applied in dispersed form, by roller coating, spray coating, slush coating or dip coating substrates such as metal, paper, paperboard and the like. These powders are also widely employed in conventional powder lining and powder molding processes such as rotational molding. Other applications of the powders of the '977 patent include use as an additive in paper pulp manufacture, as mold release agents, as additives to waxes, paints, caulks and polishers, and as binders for non-woven fabrics. There is no suggestion in the '977 patent of using these particles as catalyst supports.
It is apparent from the above remarks that a new organic polymeric support, which provides the advantages associated with such supports but which overcomes the low catalytic productivity associated with many polymeric supports in the prior art, would be highly desired.